DCF in Plain English
The Hook
A dollar next year is worth less than a dollar today, and a dollar in ten years is worth a lot less. A discounted cash flow, or DCF, turns that simple truth into a way to value almost anything that produces cash. It looks intimidating. It is not. Once you see the one idea underneath it, you will never be bluffed by a DCF again.
Plain English
A DCF values a business by adding up all the cash it will produce in the future, then adjusting each future amount for the fact that future money is worth less than money today. Why is future money worth less? Because money today can be invested to earn a return, and because the future is uncertain. So we discount future cash: we shrink it back to what it is worth in today's terms, called its present value. The rate we use to do the shrinking is the discount rate, and for a whole company that rate is usually the WACC, the Weighted Average Cost of Capital, which blends the cost of the company's debt and the cost of its equity into one number. The higher the discount rate, the harder we shrink future cash, and the lower the valuation. Add up the present value of every future year's cash and you get the NPV, the Net Present Value, which is the DCF's estimate of what the business is worth today. The whole method rests on one idea: future cash is real, but it is worth less the further away and the riskier it is.
The Math
The engine of a DCF is the present value formula. To find what a future amount of cash is worth today, you divide it by one plus the discount rate, raised to the number of years away it is. Do that for each year, add the results, and you have the Net Present Value. We use a round 10 percent discount rate below to keep the arithmetic clean.
- Present value = future cash / (1 + discount rate) raised to the number of years away
- Net Present Value (NPV) = the sum of the present values of all future cash flows
- Discount rate for a whole company is usually WACC, which blends the cost of debt and the cost of equity
Imagine you are promised 110 dollars one year from now, and the right discount rate is 10 percent. What is that worth today? Present value = 110 / (1 + 0.10) = 110 / 1.10 = 100 dollars. So a promise of 110 dollars in a year is worth exactly 100 dollars today at a 10 percent rate. The logic is reversible: if you had 100 dollars today and earned 10 percent, you would have 110 dollars in a year. Discounting is just that idea run backwards. Now push it out two years: 121 dollars promised in two years is worth 121 / (1.10 x 1.10) = 121 / 1.21 = 100 dollars today. The further out the cash, the more we shrink it.
A small business will produce 100 dollars of cash in year one, 100 in year two, and 100 in year three. The discount rate is 10 percent. Discount each year back to today. Year 1: 100 / 1.10 = about 90.91 dollars. Year 2: 100 / 1.21 = about 82.64 dollars. Year 3: 100 / 1.331 = about 75.13 dollars. Add them: 90.91 + 82.64 + 75.13 = about 248.69 dollars. So three years of 100 dollars each is worth about 248.69 dollars today, not 300, because future dollars are discounted. That total, about 248.69 dollars, is the Net Present Value of those cash flows.
Take the same three years of 100 dollars each, but now use a 20 percent discount rate instead of 10 percent, because the business is riskier. Year 1: 100 / 1.20 = about 83.33 dollars. Year 2: 100 / 1.44 = about 69.44 dollars. Year 3: 100 / 1.728 = about 57.87 dollars. Add them: 83.33 + 69.44 + 57.87 = about 210.64 dollars. Compare that to the 248.69 dollars we got at 10 percent. The exact same cash flows are worth about 38 dollars less simply because we judged the business riskier and used a higher rate. This is the most important lever in any DCF: a higher discount rate means lower value, and small changes in the rate move the answer a lot. When someone wants a DCF to say a bigger number, the discount rate is the first place they reach.
The Lingo
- DCF (discounted cash flow)
- A valuation method that adds up a business's future cash, with each amount shrunk to its value today.
- Present value
- What a future amount of cash is worth in today's terms after discounting.
- Discount rate
- The rate used to shrink future cash to present value. A higher rate means lower value.
- WACC (Weighted Average Cost of Capital)
- The blended cost of a company's debt and equity, commonly used as the discount rate for the whole business.
- NPV (Net Present Value)
- The sum of the present values of all future cash flows. The DCF's estimate of value today.
- Terminal value
- An estimate of all the cash a business produces beyond the years you forecast in detail, discounted back to today.
- Time value of money
- The core idea that a dollar today is worth more than a dollar in the future, because it can earn a return and the future is uncertain.
Practice
In the Room
The Trap
Believing the DCF's precise number. A DCF produces an exact-looking figure, but it is built on assumptions, and the discount rate especially can swing the answer enormously. Nudge the rate up or down a couple of points, or tweak the long-term growth in the terminal value, and the valuation moves dramatically. The fix is to never quote a single DCF number as truth. Run it at a range of discount rates, see how much the answer moves, and treat the output as a range shaped by your assumptions, not a fact.
Quick Check
Q1.What is the core idea a DCF is built on?
Q2.You are promised 110 dollars in one year and the discount rate is 10 percent. What is the present value?
Q3.If you raise the discount rate, what happens to the DCF valuation?
Q4.A business produces 100 dollars in year one and 100 dollars in year two. At a 10 percent discount rate, what is the NPV (rounded)?
Q5.Why should you never quote a single DCF number as the truth?
Practice Out Loud
A founder shows you a DCF valuing their startup at 50,000,000 dollars and treats it as fact. In 90 seconds, explain in plain English how the discount rate drives that number and why you want to see it run at a few different rates. The AI will play the founder, who pushes back with: but the model is detailed and the math is correct, so why question it?
Try it in real life
Sketch a five year cash flow forecast for a small business you know well, even on a napkin.
Wrap up this lesson
Submitting the Quick Check counts. Or mark it here when you feel ready.